fix: keep reconciled and replayed lists in sync with the server

[xsmyile]

Reconcile: an in-place read kept only rows it had already loaded, so a new match between them (a message starred during a disconnect) was dropped. Replay: an arrival not on the fresh page was taken as new, but arrivals commit in order, so every one up to the last the read returned was already in its total.

Part of #129

[pullfrog]

✅ No new issues found.

Reviewed changes Reviewed the UI and TUI list synchronization changes, regression tests, and the server ordering guarantees supporting arrival replay.

• Held reconciliation: Replaces the server-confirmed loaded window, including newly matching rows between existing rows, while retaining an unresolved tail.
• Arrival replay: Uses the last returned arrival as a watermark to avoid counting earlier committed arrivals twice in both clients.
• Regression coverage: Adds exact row and total assertions for intermediate matches and arrivals beyond page or held-row limits.

Validation passed: all 155 message-store tests, all 75 TUI tests, and tsc -b. Browser tests and the full workspace suite were not run.

  ^{｜ View workflow run ｜ Using gpt-6.1-sol ｜ 𝕏}